Mechanical current converters



April 2 8, 1959 P. BRUECKNER 2,384,584

MECHANICAL CURRENT CONVERTERS Filed June 18, 1953 l? I? a a 6 L 8 -L 8 h2 x3? ,9 --:[1 a 1 '8 :T: I 5 g g" :5 g 2 5 3 Inventor? ATTORNEY UnitedStates Patent 0 MECHANICAL CURRENT CONVERTERS Paul Brueckner, Misburg,near Hannover, Germany, assignor to August Hamilton Schilling, Atherton,Calif.

15 This invention relates to mechanical current converters havingassociated therewith commutating reactors and auxiliary currentconverters connected in parallel with the disconnecting path.

The present invention has for its object to realize during thecommutation process as much as possible a sparkless opening of themechanically actuated contacts located in the disconnecting paths of thecurrent converters.

Another object of the invention is to decrease to a great extent thedimensions and the cost of commutating reactors which have been proposedalready for accomplishment of this task and which have become known inconnection with shunt current paths in parallel with the contacts of themechanical current converters.

It is a further object of the present invention to reduce the voltageeffective in the commutation circuit and determining the dimensions ofand therewith the cost of such commutating reactors.

In order to accomplish this task it has already been 35 proposed toconnect quenching rectifiers in parallel with the commutating reactorand to the mechanically actuated contact. In this case said quenchingrectifiers have been designed as dry-plate rectifiers, thyratrons andother common current converters. Such installations, however, have onlya very small overload capacity, thus requiring correspondingly highconstructional expenditure. Although a certain part of the costsresulting therefrom can be saved through the decreased expenses for thecommutating reactors, the final result does not bring forth the 1;deciding technical and economical advantage whose realization, is theobject of the present invention. This object. of the invention comprisesthe task of reducing the voltage effective in the commutating circuitdown to few hundredths of the voltages which hitherto prevailed. 5')Therewith it becomes possible to accomplish the further objective of thepresent invention that is, to design the commutating reactor as a simplecore encompassing the current conveying conductor, thus eliminatingcompletely any auxiliary winding.

All these problems, including mechanical current converters havingcommutating reactors and auxiliary current converters connected inparallel to the disconnecting path Where an auxiliary voltage source isprovided in a path parallel to the mechanically operated contacts, aresolved according to the invention by providing on the one hand,controllable current converters having with regard to current very highoverload capacity, preferably current converters whose currentconducting arc in each phase is initiated by an ignition process and isquenched through the valve effect of the current converter, and on theother hand these problems are solved by providing commutating reactorslocated only in the branch circuit of the mechanical current converterand arranged for a 0 potential corresponding to the difference betweenthe auxiliary voltage and the sparking voltage of the auxiliary currentconverter.

Consequently, in contrast to known arrangements where the commutatingreactors carry the entire main current and the shunt paths are assignedto convey the smaller current during no-load intervals caused by thecommon type of large commutating reactors, according to the inventionthe main current is cornmutated by means of an auxiliary voltage on theauxiliary current converter toward the end of the current passage time.Thus the mechanical contact has only to break a circuit in which thesmall differential voltage of auxiliary voltage and sparking voltage iseffective. Therefore, a commutating reactor of the hitherto common sizeis unnecessary. In order to facilitate the task of the mechanicalcontact, a very small commutating reactor, having a size of only fewpercent of that of hitherto common commutating reactors, is connected inseries to it. The cost of such a small commutating reactor is no longerof importance. In most cases it will be sufiicient to design thecommutating reactor as a simple iron core encompassing the currentconveying conductor, thus making it possible that eventually auxiliarywindings can be completely dispensed with.

The drawing shows by way of example a circuit according to the presentinvention. In said drawing,

Fig. 1 illustrates a circuit diagram of a three-phase oneway rectifierconstructed in accordance with the present invention; while Fig. 2 showsthe circuit of a periodically actuated ignition circuit for an ignitronserving as an auxiliary rectifier.

Mechanical contacts 2 are connected in known manner to the three phasesof the current converter-transformer 1. The circuit closes over the load3 and an eventually arranged smoothing reactor 4. Highly overloadableand controllable current converters, for example, ignitrons 5 andauxiliary voltage sources 6 are shunted across the mechanical contacts2. Besides this, commutating reactors 7, of extraordinarily reduced sizewhen compared with commutating reactors of known design are provided inthe current branch of the mechanical contacts. Additionally to eachswitch contact 2 of the main circuit, there is provided in each case arotatably arranged switch bridge 2 having the contact parts 8 andactuated by means of the driving device for the main contacts 2. Thecontact parts 8 bridge momentarily and periodically the auxiliarycontacts 9 which are in the ignition circuit of an ignitron 5 whosecircuit is illustrated by way of example in Fig. 2.

Fig. 2 shows the transformer 11 which charges a condenser 10 by way of avalve 12 so long as the contact bridges 2' do not connect the auxiliarycontacts 9. If, however, the contacts 9 are bridge, then the condenserdischarges over the ignition point of the ignitron and there effects theintroduction of an arc.

The manner of operation of the circuit is as follows:

The mechanical contact 2 associated with a phase is closed during thelongest period of the current passage time through said phase and theshunted auxiliary current converter is opened thus allowing the currentto flow over the mechanical contact 2 only. The auxiliary currentconverter 5 is ignited at a desired moment towards the end of thecurrent passage time. Toward the end of a current passage period theauxiliary current con verter 5 is ignited by momentary actuation of theauxiliary contact bridge 2 which occurs at a predetermined advance withrespect to the moment of opening of the main contacts 2, as theauxiliary contacts 9 are momentarily connected through the auxiliarycontact bridges 2. The discharge current circuit for the fully chargedcondenser 10 is thereupon closed and the ignition of the arc in theassociated ignitron is initiated. The auxiliary voltage source in thiscase must be proportioned in such manner that it covers the sparkingvoltage of the auxiliary current converter 5 and is capable of commutingthe main current from the mechanical contact to the shunted auxiliarycurrent converter Within an appropriate interval of time which may rangeapproximately from 5 to electrical degrees. After the main current hasbeen taken over by the auxiliary current converter 5, a low voltage,caused by the difference between auxiliary voltage (voltage source 6)and sparking voltage of the auxiliary current converter 5, applies tothe series connection of the main contact 2 and the commutating reactor7. The commutating reactor 7 now makes possible the practicallysparkless opening of the contact 2.

As has been already mentioned above, the commutating reactor 7 onlyneeds to be dimensioned for the indicated very small differentialvoltage.

In the embodiment illustrated, ignitrons are shown as auxiliary currentconverters. However, other arrange ments or types as, for example, aretype current converters may be used as auxiliary current converters. Adetermining fact is their high overload capacity with regard to current,as otherwise uneconomically large arrangements would become necessary.

It is not necessary, as shown in the drawing, to design the auxiliaryvoltage sources 6 as independent transformers. On the contrary, it issuflicient, if, for instance, the main transformer is provided withadditional terminals for tapping the auxiliary voltage.

There is the further particular advantage with the arrangement proposedaccording to the invention that, as already has been mentioned, themoment of ignition of the auxiliary current converters can be chosenabsolutely according to desire. If the moment of ignition of theauxiliary current converter is kept constant with time in relation tothe opening moments of the mechanically actuated contacts, thecontacting duration of the mechanical contacts 2 can remain constantwithout regard to modulation and load condition of the mechanicalcurrent converters, thus saving a considerable amount of expense forregulator installations.

For the ignition of the additional current converter there are availablestill other electrical circuits diifering from that shown in Fig. 2 andin themselves known, which circuits can operate in accordance with thetype and construction of the auxiliary current converter also withoutadditional contacts. The arrangement illustrated in the drawing ofignitrons in combination with additional auxiliary contacts represents acircuit which can be realized at small expense.

I claim:

1.. Mechanical current converter comprising in combination: mechanicallyactuated circuit breaking contacts provided in the current conveyingphase lines of the current converter, current paths arranged in parallelwith the current breaking contacts, controllable auxiliary currentconverters arranged in said parallel paths, said auxiliary currentconverters being effective in the same direction as the currentconverter itself and being connected to be periodically traversed byoperating current prior to and during the commutation, said auxiliarycurrent c0nverters being constructed as current converters having highcurrent overload capacity, means for producing an auxiliary voltage inthe parallel paths, said auxiliary voltage being only slightly greaterthan the sparking voltage of an auxiliary current converter, andcommutation reactors arranged only in the current branch of themechanical current converter, said commutation reactors being di--mensioned for a voltage equal to the difference between the auxiliaryvoltage and the sparking voltage of an auxiliary current converter.

2. Mechanical current converter according to claim 1,

including means for initiating current-conducting arcs in each phase byan ignition process and for extinguishing the arcs by valve actions ofthe current converter.

3. Mechanical current converter according to claim 2, wherein saidcommutation reactors consist exclusively of an iron core encompassingthe current conveying conductor.

4. Mechanical current converter according to claim 1, including meansfor igniting the auxiliary current converter at the end of the passagetime of the operating current.

5. Mechanical current converter according to claim 1, including meansfor initiating current-conducting arcs in each phase by an ignitionprocess and for extinguishing the arcs by valve actions of the currentconverter, said auxiliary current converters being constructed asignitrons.

6. Mechanical current converter according to claim 1, including meansfor initiating current-conducting arcs in each phase by an ignitionprocess and for extinguishing the arcs by valve actions of the currentconverter, said auxiliary current converters being constructed as arccurrent converters.

7. Mechanical current converter according to claim 1,

' including means for initiating current-conducting arcs in each phaseby an ignition process and for extinguishing the arcs by valve actionsof the current converter, and control means adapted to keep the momentsof ignition of said auxiliary current converters at a constant timeinterval from the moment of opening of the mechanical contacts.

8. Mechanical current converter according to claim 1, including meansfor initiating current-conducting arcs in each phase by an ignitionprocess and for extinguishing the arcs by valve actions of the currentconverter, and means for keeping constant the duration of mechanicalcontacting independently of the modulation of the current converter.

9. Mechanical current converter according to claim 1, including meansfor initiating current-conducting arcs in each phase by an ignitionprocess and for extinguishing the arcs by valve actions of the currentconverter, and means for keeping constant the ignition of the auxiliarycurrent converter in relation to the moment of opening of the mechanicalcontacts, said constancy being adapted to keep constant the opening ofthe contacts of the mechanical current converter independently of theload current.

10. Mechanical current converter according to claim 1, including meansfor initiating current-conducting arcs in each phase by an ignitionprocess and for extinguishing the arcs by valve actions of the currentconverter, and auxiliary contacts on said current converter adapted toignite the auxiliary current converters.

11. Mechanical current converter comprising in combination mechanicallyactuated circuit breaking contacts provided in the current conveyingphase lines of the current converter, current paths arranged in parallelwith the current breaking contacts, controllable auxiliary currentconverters arranged in said parallel paths, said auxiliary currentconverters being effective in the same direction as the currentconverter itself and constructed as current converters having highcurrent overload capacity, means for producing an auxiliary voltage inthe parallel paths, and commutation reactors arranged only in thecurrent branch of the mechanical current converter, said commutationreactors being dimensioned for a voltage equal to the diiference betweenthe auxiliary voltage and the sparking voltage of an auxiliary currentconverter, and means for initiating current-conducting arcs in eachphase by an ignition process and for extinguishing the arcs by valveactions of the current converter, said means for producing an auxiliaryvoltage consisting of independent transformers.

5 12. Mechanical current converter comprising in combination:mechanically actuated circuit breaking contacts provided in the currentconveying phase lines of the current converter, current paths arrangedin parallel with the current breaking contacts, controllable auxiliarycur- 5 the sparking voltage of an auxiliary current converter, 15

means for initiating current-conducting arcs in each phase by anignition process and for extinguishing the arcs by valve actions of thecurrent converter, and a current converter transformer, said means forproducing an auxiliary voltage in the parallel paths consisting ofauxiliary terminals on the current converter transformer.

References Cited in the file of this patent UNITED STATES PATENTS 102,610,231 Wettstein Sept. 9, 1952 2,619,617 Pakala Nov. 25, 1952 FOREIGNPATENTS 221,725 Switzerland Sept. 1, 1942 911,544 France July 10, 1946

